linux-kernel - Re: AMD Quad Core clock problem?

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Date:	Thu, 17 Apr 2008 11:03:04 -0700 (PDT)
From:	Marc Perkel <mperkel@...oo.com>
To:	Bart Van Assche <bart.vanassche@...il.com>
Cc:	Chris Snook <csnook@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: AMD Quad Core clock problem?


--- Bart Van Assche <bart.vanassche@...il.com> wrote:

> On Wed, Apr 16, 2008 at 11:44 PM, Marc Perkel
> <mperkel@...oo.com> wrote:
> >  --- Bart Van Assche <bart.vanassche@...il.com>
> wrote:
> >  > It's better to correct the clock frequency once
> with
> >  > the tickadj or adjtimex, so you don't have to
> add
> >  > ntpdate to cron and you can still run ntpd.
> >  >
> >  > Bart.
> >
> >  ok - thanks. How do I do that?
> 
> You can do that as follows:
> * First of all, make sure that adjtimex is
> installed. Some distro's
> include this command in util-linux.
> * Query the current tick value via adjtimex -p |
> grep tick. E.g. with
> HZ = 100, tick == 10000.
> * Multiply the tick value with the relative clock
> error: when e.g. 3s
> are lost every hour, the correct tick value is 10000
> * (1 + 3/3600) =
> 10008.
> * Pass this new tick value to the kernel via
> adjtimex -t 10008.
> * Stop and restart ntpd such that it forgets any
> previous frequency estimates.
> * Keep an eye on the output of adjtimex -p|grep
> frequency to see
> whether the frequency estimate converges (should be
> stable within 10
> ppm after an hour. See also man adjtimex for the
> units of this value).
> 
> Bart.
> 

Thanks Bart - that seems to have worked. A value of
10025 seems to get it close enough for NTPD to lock
on. I'm using tickadj.

So - the question is - is this a kernel bug not
calibrating quad core phenoms right or do I just have
a bad motherboard?



Marc Perkel
Junk Email Filter dot com
http://www.junkemailfilter.com


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